The problem as pointed out by the author in the link, is that there simply is no storage solution that sits between a SATA HDD (cheapest 0.15 Euro/TB) > NVME (0.45 Euro/TB).

Technically, SATA SSD's need to fill this spot as a cheaper alternative but with their prices being just as expensive (often only 5% cheaper) as m.2. If SATA had a price range in the 0.30 EUro/TB, it will have been a great alternative to HDD based storage.

And you can go really crazy with bifurcation > 4/4/4/4x and then converting all those new m.2 slots to 6 SATA (ASM controller for cheap and work great). Plop, 24 SATA ports for 4W power draw.

But nobody is going to pay for SATA SSD's when they can just buy m.2 for the same price. So the result is that the SATA SSD market is "kind of dying", and manufactures look at it like 2.5" drives got looked at from HDD manufactures.

It does not make sense for SATA SSDs to be priced 1/3 cheaper than NVMe as they use the same NAND flash as NVMe drives. NAND flash is a commodity so doing artificial segmentation with it is tricky. Controllers, I imagine, are cheaper since SATA is capped at 6Gbps (much lower than NVMe) but even if a SATA controller were half the price of a top end NVMe one, the controller would need to constitute 2/3 of the BOM cost of the SSD to enable a price reduction like that, which it does not.

Not the problem the author is pointing out (otherwise paying extra for an M2<->SATA adapter would be stupid). It's that the price of a SATA hard drive with capacity > 4TB is more (sometimes a lot more) than the price of an NVME hard drive of the same capacity.